The Republic of Ireland Act comes into force, declaring Éire to be a republic and severing Ireland's "association" with the Commonwealth of Nations.

The Republic of Ireland Act 1948 is an Act of the Oireachtas which declares that the description of Ireland is the Republic of Ireland, and vests in the president of Ireland the power to exercise the executive authority of the state in its external relations, on the advice of the Government of Ireland. The Act was signed into law on 21 December 1948 and came into force on 18 April 1949, Easter Monday, the 33rd anniversary of the beginning of the Easter Rising.